Currently, urologists performing a procedure known as percutaneous nephrolithotomy (PCNL) often use a rigid nephroscope, a flexible cystoscope, or a flexible ureteroscope in conjunction with flexible baskets or graspers to remove stones and stone fragments from the renal cavity of a patient. A rigid or semi-rigid scope is often used to treat the lower urinary tract, while accessing upper urinary tract needs a flexible scope for negotiating the tortuosity when the ureter crosses the iliac vessels. Because of the high degree of deflexibility required for a scope to travel to the upper urinary tract, in terms of both active and passive deflection, adding accessories to the working channels of a flexible ureteroscope, which compromises the scope's overall deflexibility, is often undesirable. See, Smith's Textbook of Endourology, Vol. 1, Ch. 32 (1996, Quality Med. Pub. Inc.).
To remove stones and/or stone fragments, urologists generally use an endoscope coupled with accessories such as baskets or graspers. The use of accessories in the working channels of the endoscope becomes problematic when it comes to treating upper urinary tract because of added constraints on the scope's deflexibility and hence access to the target. Also, using a basket or grasper through a flexible scope can be technically challenging due to the high level of manual dexterity required of an operator to manipulate effectively the basket or grasper to capture and retrieve the stone(s) and/or stone fragment(s). Procedures that use baskets or graspers also are time-consuming since the entire scope must be retracted to remove stone(s) or fragment(s) from the renal cavity. If there are multiple stone(s) or fragment(s) to be removed from a specific area, then every time a flexible scope is retracted, the urologist must maneuver his/her way back to the desired location to get the next stone or fragment. This obviously increases the level of tissue trauma to the patient and the risk of damage to the urinary tract.
Urologists also use lithotripters to crush stones into fragments that are passable through the urinary tract. Lithotripsy devices have been developed which utilize electrohydraulic probes, ultrasonic probes, electromechanical impactors, laser fibers and so on. An example of a lithotripter is a system known as “Lithoclast” that is commercially available from Boston Scientific Corporation of Natick, Mass. Again, the addition of a lithotripter will compromise the scope's deflexibility and thus will limit its use in treating the upper urinary tract. Such limitation also affects the breaking power of a lithotripter and renders treatment of upper urinary tracts longer and less successful.
Suction channels, sometimes with a lithotripter in a parallel working channel, have been integrated into scopes to help remove stones and fragments. For instance, a suction system known as “Lithovac,” also available from Boston Scientific Corporation of Natick, Mass., can be matched with the “Lithoclast” lithotripter system to remove stones and/or stone fragments from the renal cavity of a patient during a PCNL procedure. Because an integrated suction channel will further decrease the deflexibility of a flexible scope, the use of lithotripters with integrated suction is limited to renal areas that can be accessed by a rigid device. And even in such cases, the suction channel is often highly limited in its diameter and hence the suction capacity.